Mould on cannabis is hardly a new issue; it is, in fact, something that cannabis growers have been battling since they started growing cannabis.

Mould growth can be attributed to moist growing conditions and humidity during the curing process, which is when the flower is dried and prepared for consumption. Properly curing cannabis can lead to higher potencies and better preserve terpene profiles, which can produce a more flavourful and aromatic experience.

The number one factor contributing to development of mould is moisture control, says Jodi McDonald, president and founder of Keystone Labs.

“If the producer can control the mould in the process, there will be no mould in the product. They do that through moisture control and through process control,” McDonald explains. “Key parts of process control include: HVAC (heating, ventilation and air conditioning) design, personnel hygiene, clean-out procedures between batches and the flow of materials (in and out of grow rooms),” she adds.

Sometimes precautions fail, and mould grows

Licensed producers operate in a highly regulated industry and cannot allow contaminated cannabis products to ship to consumers. At this time, using gamma radiation appears to be the only viable option available to LPs when it comes to eliminating mould found on cannabis.

To the uninitiated, this may sound unnerving and controversial, but in reality, the process is fairly benign and far better for consumers than ingesting mouldy cannabis.

Radiation is a broad term for transferring energy. Irradiation, aka gamma radiation, has been used in food and medicine production for decades, where microbial contamination must be reduced or eliminated.

It is said to be a much healthier alternative to using pesticides and fungicides. Data shows that pesticides can be detected in the liver and bloodstream after a consumer smokes cannabis that had been exposed to pesticides.

There are others, but chronic pulmonary aspergillosis or CPA is an example of a contamination caused by inhaling fungal spores that enter the bloodstream. This causes infection and has, in rare cases, such as with a patient who has a compromised immune system, proven to be fatal.

Cannabis flowers are far too dense for a decontamination treatment such as pressure, heat or steam—which is how hospitals sterilize surgical equipment—to penetrate deeply enough to be effective. Using heat, steam and pressure would result in soggy cannabis flowers, rendering them useless and unsaleable.

That being the case, taking a page out of the Food safety standards and guidelines, LPs have turned to irradiation, something that has been endorsed for safety by Health Canada, the World Health Organization and the U.S. Department of Agriculture.

What is irradiation?

Irradiation is when highly energetic light (photons) is targeted directly at a material—in this case, dried cannabis flower. The DNA strands present in the existing microbes become so damaged as a result of exposure to the photons that they can no longer multiply and will perish. At this point, the cannabis flower’s plant cells have already been harvested and cured (dried) so the irradiation only kills the microbial growth with very little change to the cannabis being observed, notes a study conducted in 2016 by Bedrocan International BV, Veendam, Netherlands.

There are some case studies that indicate that terpenes may be affected by gamma radiation. Cilantro leaves, for example, were shown to lose some terpenes (those known for their sedative and anti-inflammatory effects) content following the irradiation process, so it’s entirely possible the same could be said for cannabis.

In general, though, there is thought to be no inherent safety risk in ingesting a cannabis product that has been irradiated.

Gill Polard is the co-host of the High Friends podcast and the creator of The Her(B) Life website and magazine, which celebrates the feminine cannabis experience through industry interviews, essays and stories.

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